The invention resides in a biopsy device for the removal of soft tissue samples from a living organism including a housing supporting a biopsy needle with recesses in its sides near the tip of the needle, a cannula which is axially movably disposed on the needle, a spring for moving the needle forwardly and a spring for moving the cannula forwardly.
In human and veterinary medicine, a targeted removal of soft tissue samples from the living organisms, called biopsy, is a solid part of the diagnosis in connection with numerous health problems. Often, only the examination of a tissue sample permits a safe diagnosis. Whereas a biopsy is performed usually on body parts which are accessible from the outside by surgical instruments, endoscopic procedures must be used for biopsies on internal body parts using for example a biopsy needle. The biopsy needle, which has a recess at its side near its tip, is inserted into the tissue to be examined so that the tissue enters the recess. Then a cannula is moved forwardly over the recess toward the needle tip whereby the tissue in the recess is severed and removed with the needle for examination.
There are three different types of biopsy devices. In manual biopsy devices, the needle is normally inserted and the cannula is manually moved forwardly. In semiautomatic biopsy devices, the needle is manually inserted, but the cannula is moved at high speed forwardly over the recess of the biopsy needle by the release of a compressed spring. Automatic biopsy devices include generally two spring force storage structures, one for the rapid forward movement of the biopsy needle into the predetermined target area and the other for the immediately following rapid forward movement of the cannula.
WO96/39941 discloses an automatic biopsy device which comprises a housing with a biopsy needle and a cannula supported therein so as to be axially movably disposed on the biopsy needle. It also includes for each a spring structure with a metal spring for a spring force driven forward movement of the biopsy needle and the cannula. For the automatic operation, first both springs are manually compressed or tensioned, whereby two guided members, on which the biopsy needle and the cannula are mounted, are retracted to an end position in which they are compressed or tensioned. Two guided members on which the biopsy needle and the cannula are mounted are retracted thereby to an end position where they are held by a simple locking mechanism disposed eccentrically with respect to the cannula and the biopsy needle. After the biopsy device is properly positioned, the locking mechanism for the biopsy needle is released whereby the needle is propelled by spring force toward the target area. Shortly before reaching the target area, the movement of the biopsy needle releases in the housing the locking mechanism for the cannula resulting in a spring force operated advance of the cannula. However, the biopsy device includes several metallic components, which are for example springs consisting of spring steel. This causes in the MRT picture distortions (artifacts) Steel springs are consequently not very suitable for use with MRT. The biopsy needle with the cannula is provided in the form of a replacement unit in the housing with the two spring force storage structures.
However, if during an MRT examination a carcinoma is detected and if based on the image, a tissue sample is to be taken in the MRT, the biopsy device and the manipulator must be of such a design that no artifacts occur.
It is the object of the invention to provide a biopsy device with a spring force storage arrangement so that it is suitable for an image-based operation with an MRT in which strong magnetic fields (>1 Tesla) are present. Furthermore, the kinematics of the biopsy device should be improved so as to facilitate the replacement of the biopsy needles and cannulas and to improve generally the operation of the device.